Rectifying apparatus.



0. A. KRAUS.

RBGTIFYING APPARATUS. APPLICATION FILED NOV.21,1910.

Patented Feb. 3, 1914.

'-1nore anodes and a UNITED STAflJES T OFFICE.

CHARLES A. KR AUS, DE -NEWTON HIGHLANDS, MASSACHUSETTS.

RECTIFYI NG APPARATUS.

To a ta /10m it may com c/'11.

Be it known that '1, CHARLES A. Keane, a citizen of the United Statesand resident oflYcwton Highlands, in the county of Middlesex and Stateoi Massachusetts, have invented new and useful Improvements inRectifying Apparatus, of which the following: is a specification.

My iny'ention relates to vapor electricapparatus and has for its objectthe provision of such circuit and distribution arrange Incnts aswill'minimize and practically eliminate the difliculties and dangers dueto short circuit arcing in the exhausted containers of such apparatus.

For illustration otmy invention 1 take the mercury arc"rcctitie* as acha act-cristie example of vapor electric apparatus in the operation ofwhich short circuit arcing has heretofore proved a source of difficultyand of actual danger to the structure and integrity of the ap iaratus.As is well known, a mercury arc rectifier consists essentially of ahighly exhausted envelop or container within which are provided two or.mercury cathode, the anodes being C()I1Sll'tl(l0(l usually of solidconducting materials. The anodes being connected respectively to theouter terminals of a suitable exciting rcactance and the midorneutral-point of the reactance being connected through a load circuit tothe mercury cathode, the anodes allow the current to flow through therarefied vapor in the container to the mercury cathode but refuse toallow current to flow in the reverse direction under normal properworking conditions. Ilv this check valve action, only one- -half wave ofthe impressed alternating current, flows through either anode and thetwo half waves succeed each other by phase differences of .180" andcombine in the load circuit to Form a continuous, pulsatincunidirectional currcnt ot which the wave :lorm is dependent upon thercactance in the load circuit.

For reasons which are not yetwell understood, it, often happens that thecheck alve action 01 an anode tails to manifest itself, so that thecurrent instead of flowing in the proper normal manner flows from oneanode to the other. Since there is no can Specification of LettersPatent.

Application filed November 21. 1910.

Patented Feb. 3, 1914. Serial No. 593,297.

sidcrable impedance in the circuit when the current passes between theanodes, the current not only is the proper operation of the ap paratusinterrupted but, what is more Serious, the integrity of the apparatusitself is endangered. This phenomenon is known as short circuit arcing.Although attempts have been made heretofore to prevent short circuitarcing by increasing the length of path between the anodes, this has notproved effective since the tendency to are increases both with increaseof potential and current, and short circuit arcs inevitably occur inrectifiers of comparatively large energy-capacity. For this reason theutilities of mercury are rectifiers have been greatly restricted.

My invention is characterized bV the in troduction into rectifiercircuits of opposed, and, preferably, accu 'ately balanced reactances insuch manner that under the normal operating conditionsthese reactancesdo not affect the current to any practical degree but so that they mayact as control reactances to keep the current below a predetermined safevalue in case a short circuit are should occur.

In the drawing: hereto annexed there is illustrated in diagram anapparatus which exemplifies this invention inits application to therectification of a single phase alternatin; current. y Y

Referring to the diagram, A, A. represent; mercury arc rectifiers of theusual construction in which I), E and I) E are the main or workinganodes, (l and C the mercury cathodes and If and I the auxiliary orstarting anodes. The starting anodes may be put in circuit with a sourceofcoutinuous unidirectional controlled by resistance .imlicated at lland B. This portion of the apparatus'is provided merely for starting itand my iinproveincnt is not concerned with it. The reactances whichrepresent the sources of alternatingcurrent for the two rectitiers A andA are represented by L, R, and L, R. These rcactances are substantiallyidentical, and are so formed and associated with a source of alternatingcurrent that the terminal poles L, L and R .s respectively are reachesabnormally high Values so that current as K which may be suitablysimilar in respect to current-direetion.- The reactanccs L R and L R maythus he. encrgized inductively by coils T and T from altei'nat-ingcurrent mains M M. Between the source reactances and the rectificrs Iprovide nnitually opposed, balanced, or neutralizing reactances P, Q,and P, Q; rcspectirely. the inc nbcrs of each of these pairs beingassociated through'a magnetic circuit 0, O, respectively. The cathodes Cand Cf of the two rectitiers A and A" are connected in parallel through.lines 1 t, to the line in which the load H is interposed and from theline 5 to the mid points of the souree-rcactances in parallel throughlines 5 a, s. The main or working anodes of each rectifier are connectedrespectively to the outer terminals of one 01' the'sourcereactspectively through lines Z, 1", to the outer terminals ot' theexciting reactance L, -r, the anodes D and E are connected respectirelvthrough the lines Z, r, to the outer terminals oi theXCltlllQ'lCfiCl'tUlCQ L, R.

The line Z includes the governing react ance P and the line Z includesthe rea'etance Q which is opposed. to or balanced by the reactance 1Likewise the line '1 includes the rcactance P and the line r thereactance.

Q, so that the lines or connections rein magnetically similar terminalsof the two exciting reactances pass through gor'crning r. actances whichare prct'e ably perfectly balanced.

Assume now that the entire apparatus is in operation to rectify singlephase alternating current converting it into a pulsating unidirectionalcurrent through the load ll. During a one-half phase current will D andE being connected rewhilemutually opposed and rcnl lion's from theopposite terminals oi. the exciting reaclaiares through line 7-, a",that is. the magnetic circuit 0. to), are each altcrnatirely working andidle, as the are cnergized in parallel from not. \Vhen, however, thenext hall phase is established, the check valve action of anodes 1)and 1) comes into play, lines 1. and Z become inactive and the currentflows through 1', r to anodes E and E, cathodes C and C, and thence asbefore through t, Z through load H, line S and lines s,,s to themid-points ot the exciting reactanccs.

Under the above described normal working conditions, the governingreactances P, Q or P, Q as the case may be, oiiset and the two sources.or I 3 tential wave during the hall cycle is i preaching its maximum.value.

l l l cuit arcing in the two rectilicrs. Only in the .in so doingClQVGlOP' the -lull reactive power of the Widing and, since the in fcascof current in winding P, due. to the short cir O cult supposed is notaccou'ipanied by corresponding increase in the wining (-1,, teedingthewinding 1), the diilerence in the current values in P and (Qt mustturtherrnor overcome the unbalanced reactive power-of the winding P,acting in series W. "h 3 t limit the current flow. "lhe dangerourheretofore possibly destructive action o short circuit are is thereforesuppressed the apparatus preserved from injury. i such a short circuitare in one of the r liers A, A, the establishment of the nes halt cyclewill cause the rectifier to resume its normal operation,

The only condition in such an apparatus as herein described under whichshort cir cuit arcing can cause undesirabl or (lain gerous high currentsto iiow through the that of Sli'DillliZtIlQOllS short cir- Cirrectifiers 1s 100 case of the chccl-z valve action oi, say, anodes I)and D ceasing to function siinultancously can the current due to shortcircuit arcs reach abnormally high "values.

The phenomenon of short circuit arcing occurs in (i-rectifier oranalogous apparatus at intervals which depei'idcn the construction ofthe rectifier, and also on the. current and potential and when it occursit endures at the 11108, for half a cycle in a. properly designedapparatus. Therefore, to enable slrort circuitarcing to producealniornially or dangerously high clu'rents in an apparatus arrangedaccording to this invention, the short circuit arcing inust coincide inthe two rectiliers within a period of time considcrihl less than thatoccupied by a halt cycle, since it is sale to a rmic that the shortcircuit are is produced only when. the poan" vGut in th'-- der todemonstrate the practical lll'lflll! of an apparatus such above desc"from the dangers of short circuit are let us assume that thisPllGIlOllltiilUIl occur at any time during an entire wave period; andlet i a. suine also the apparatus is i single phase alter I more, inorder to he as tar 1,ose,soo

safe side in this calculation, let us assume the rectifiers to be'soconstructed that either of the rectifiers will short circuit on theaverage of once in 15 minutes. Then the probability of a short circuitare taking place in any one-half cycle in either of the rectifier-sisrepresented' by the fraction:

Then if two rectifiers of this kind are working under the conditionsnamed, the probability that the short circuit arcs in the two rcctilierswill coincide in any given half cycle is represented by the fraction:

Otherwise expressed, short circuit arcs may be expected to coincide onthe average once in 108 x10 cycles, br one coincidence in JJTQXIO"minutes, or 1120 days of 24 hourseach. In other words, the applicationof my invention lengthens the mean period of dangerous arcing from oncein 15 minutes to something over once in three years. For commercialpurposes this practically eliminates arcing as a factor of 0pcration,because at the present time no rec- 'til'icrs on the market have a lifewhich approaches three years. bo far as I am informed the life ofpresent connncrcial rectiliers averages about 1200 working hours.

It should be noted that the introduction of the above describedinvention does not de rease the elliciency ot' a rectifying sys tembecause the capacity of the system is doubled while the governingrcactanres have no seriousinl'hience on the ellicicncy ol' the system,since only their ohmic resistance is normally operative.

' What I claim and desire to secure by Let lcrs latent is:

1. ln apparatus for rectifying alternating currents, two completerectifying units, two sources of alternating current, two pairs ofmutually opposed. rcarlau es, lead: from similar tcrn'iinals of thealternating current sources passing rcsiwmively through muluallyopposed. rczu iancc-nicinl'lcrs and thence, one to an anode o'l onerectifying unit, the other to an anode of the other rcctilying unit, anda connection common to the calhodes of the two rectifying units topoints neutral with respectto tl alternating current sources.

2. In a vapor electricapparatus, two con; tainers, each having a cathodeand anodes, two sources of ahcrnal ing current, two pairs of mutuallyopposed reactances, leads from similar terminals-of the alternatingcurrent sources passing respectively through inututerminals of thesource reactances passingrespectively each through one of a pair ofmutually opposed rcactance. members, and thence one to an anode of onecontain r, the other to an-anode of the other-c0ntainer, and aconnection common to the two cathodes, and to the mid-points ofthe'source reactances. 4

4. The combination with transforming ap paratus comprising two secondarywindings,

oftwo current rectifiers connected to said" windings, and two impedancedevices each comprising two windings that are respec-.

tively interposed in the connections between the reotifiers and thesecondary Windlngs of the transformers, the connections to eachrcctilicr including a winding of each impedance device. 5.Thecombination with transforming apparatus comprising!wo secondarywindings, of two current rcctilicrs connected to said windings, and twoimpedance devices each con'iprising two normally com )lcmcntary windingsthat are res 'iertivcly interposed in the connections between thercctitiers' and the secondary windingrs' ol the transl'ornicrs, theconnections in each rectifier including! a winding of each impedancedevice.

Signed by me at Boston, \lassaclnisctts, this 3rd day of November, 1910.

CHARLES A. KRAUS.

\Yil ucsses:

(nannies l). iVoonm-ann', ()mN Honours.

